Biscuits V Domino's = strength ?

[Blister]

Biscuits V Domino's = strength ?

When in my local hair dressers ( Yes I have a small pelmet of hair left )

Richard the barber ( also a woodie ) passed a comment regarding Biscuit joints

His opinion is that a Biscuit adds no strength to a joint ? and is only an alignment aid and its the glue you use that gives the joint its strength ?

However he also recons the Domino does add strength ?

and lastly he does not own a domino

Any comments on this for my return to the chair :mrgreen: :mrgreen:

 

[Chems]

I think they do add strength. I think possibly the domino adds more. But a lot of people used biscuits like dominos before the domino was about (me included)

I have a few cabinets pre domino that are held together with just biscuits and glue.

 

[Shane]

I don't know how a biscuit could not add strength, it's a mechanical joint on an otherwise straight glue line, I use them all the time on different stuff, and if I just used glue I would expect things to fall apart in certain instances

 

[Mike Wingate]

Looking on the Dowelmax site. There is a demo vid showing comparisons of 6 types of techniques for joining wood at right angles. It seems that muitiple dowels with the Dowelmax are better. Time/money/ease of use/strength. Biscuits are not a very strong joint.

 

[toolsntat]

So, do the Domino's when glued swell in thickness and wedge themselves into the hole like biscuits :?:

Andy

 

[ondablade]

I've a sneaking feeling that this is one of those 'it all depends' sort of questions. On the configuration of the joint, the way/direction it's loaded and the way the joiners are used. Most of the makers of joining systems seem to find ways to test so that their system comes out ahead...

 

[Paul Chapman]

I have done a limited amount of testing by deliberately breaking pieces joined with biscuits and the results have convinced me that biscuits do add strength - even more so when multiple biscuits are used. I've not done similar tests with Dominos but, having used them, I would guess that they would add more strength than biscuits because of their orientation in the joint.

I think you really need to test things out for yourself - so much of what you read is only opinions.

Cheers :wink:

Paul

 

[mbartlett99]

Not sure about the biscuits but Dominoes definitely add strength. First time I used them was making some bar stools - dry fitted the first one with dominoes and had to use two people and a v. large mallet to 'persuade' it to separate. Could lean back on two legs without a squeak. Shame it costs much.

 

[Chems]

Looking on the Dowelmax site. It seems that muitiple dowels with the Dowelmax are better.

Shocker!

I think they'd be almost identical the domino and doweling. Unless you wanted to get down an work out surface area but thats a bit too far.

I don't think the domino is designed to swell, If you put it in a glass of water it doesn't really swell up. Its just a long grain glue joint.

 

[Racers]

Hi,

I remember seeing a video where they tested lots of different joints but I can't find the one I remember, there are lots on line.

I have some bedside tables that are biscuited together and are doing fine, I know its not a demanding application holding the glass with my teeth in and a book :wink:

Pete

 

[Hudson Carpentry]

Biscuits DO add strength. There considered a modern day alternative to the mortise and tenon. If there a mare aligning aid then there wouldn't be specifications related to there spacing and "doubling" on thicker timbers. The fact they provide more surface area to glue, logically tells anyone strength is added. If they are just an aid to align then you wouldn't waste your glue and for the price of a decent biscuit jointer and the continue need to purchase biscuits, you would just spend your money on 4 way pressure panel cramps and save yourself time in routing slots for the biscuits and money on the biscuits themselves.

Domino's will naturally add more strength then a biscuit as there deeper slots, thicker and provide more gluing area, if they swelled they would be even better.

The above is fact so in my opinion I would say domino's are more like a modern day M&T joint, but the extra strength is rarely required and where it is. a real M&T joint should be used for the extra strength it gives over a domino. Biscuits are more then strong enough for most applications. This being the case I class the domino as a toy and suspect your hair dresser friend is trying to justify the cost of buying a domino by convincing himself the biscuit joint is some what useless. If that ain't the case he has Festool Syndrome.

 

[yetloh]

I agree that both biscuits and Dominos add strength but, for jointing panels this is superfluous extra strength because a well prepared butt joint made with a good quality glue is stronger than the wood itself. Biscuits or Dominos therefore add peace of mind or an insurance against defects in the joint itself. They also help with location and here the Domino scores because it offers greater accuracy and the possibilty of perfectly aligned panel joints which, in my experienec are rare with biscuits. I use biscuits a lot but don't have a Domino

In the context of frame jointing where a m&t would traditionally be used, I seem to remember that FWW did some tests a while back and concluded that the m&t is strongest followed by the domino and biscuits, in that order.

Jim

 

[Blister]

Thanks everyone

Next time I go for a trim up I will open the subject again :mrgreen:

This time armed with UKWorksop behind me :mrgreen: :mrgreen:

 

[Logos]

Hello All

This is my first post in the actual woodworking forum (although I have already posted in the General Chat section) so I am also taking the opportunity to say hello and many thanks for the really interesting information that you guys and gals have been submitting. It is a real treasure trove of accumulated knowledge!

Apparently there has already been a test on the strength of woodworking joints, which was carried out by the Wood magazine a few years ago. Here is the link to the video that they made: http://video.wwgoa.com/video/Woodworking-joint-torture-tes

Although they didn't test the Domino system, they did test, amongst others, the biscuit joint. They seemed to conclude that the biscuit joint was one of the weakest, but the M & T joint was the strongest. Since the Domino system is in effect an M & T joint surely this would mean that it must be stronger.

Regards

Logos

 

[Peter T]

Hello All

This is my first post in the actual woodworking forum (although I have already posted in the General Chat section) so I am also taking the opportunity to say hello and many thanks for the really interesting information that you guys and gals have been submitting. It is a real treasure trove of accumulated knowledge!

Apparently there has already been a test on the strength of woodworking joints, which was carried out by the Wood magazine a few years ago. Here is the link to the video that they made: http://video.wwgoa.com/video/Woodworking-joint-torture-tes

Although they didn't test the Domino system, they did test, amongst others, the biscuit joint. They seemed to conclude that the biscuit joint was one of the weakest, but the M & T joint was the strongest. Since the Domino system is in effect an M & T joint surely this would mean that it must be stronger.

Regards

Logos

You can't really say that the biscuit joint is weak since there is not much to compare it to.

The only biscuited joint they tested was the mitre. In that, the unreinforced joint broke at 139ibs while the same joint with a small no. 0 biscuit broke at 220lbs.

It would have been interesting to get a direct comparison between the M&T joints and the same joint with biscuits, although, for me, biscuits are much more use for joining panels.

 

[Mike Wingate]

I have just spent 2hrs building drawers with mahogany, pine and MDF parts. All have been biscuit jointed. Quick, easy to mark out. flawless. False fronts hide the grooves for the ply bases, which were cut on the rip saw. Strong enough.

 

[danielddr]

Hi,

I've seen this discussion come up on a number of forums, with the discussion frequently degenerating into quite bitter disputes between the participants. Studies, similar to the ones referenced here are normally highlighted, which show that traditional M+T joints are amongst the strongest methods of joining bits of wood together, with dominos coming close and biscuits trailing some way behind.

Personally I don't have an issue with the numbers, they broadly agree with what I'd expect. However, what I've never seen is any context placed on these numbers; how strong does a joint have to be in order to be useful? Obviously there's no single number, a joint in a chair will be subjected to a far greater load than a joint holding together a drawer. But to my mind it's this information that determines whether the use of a biscuit joint is a reasonable time saving approach to construction, or a bit of a bodge that will fail easily. Does anyone have anything figures concerning 'typical' loads joints will be subjected to that could assist in interpreting 'absolute' strength measurements?

Cheers,

Daniel

 

[Jonesy]

Biscuits definitely add strength - I've got a book with an article testing their performance for joinery for full sized doors. It compared butt joints with 2 or 3 biscuits, against tongue and groove joints reinforced with either a loose tenon or a mortise and tenon. The biscuits came out strongest with the others not far behind, the main difference was that the tenon joints failed more gracefully and the joint remained damaged but intact whilst the biscuit joint failed completely. The joints started opening at ~1000 lbs and failed at over 2000 lbs.

 

[yetloh]

But, as I and others have said before, is it useful or necessary extra strength, bearing in mind the strength of modern glues? In some cases, such as chairs you need all the strength you can get, but doors are another matter entirely.

Jim

 

[Erasmus]

Anything which increases the glueing surface area strengthens the joint, it's just a matter of degree. I still scarify board joints as well especially on dense hardwoods.